Timber jacks are well known in the industry for lifting heavy logs off the ground. However, these are generally for handling heavy timber on smooth ground and are not portable. They have many other unsolved problems, and are not suitable when it is desirable for a single person to use the jacks alone in either the woods or at a tree felling site such as in a city after a wind storm. Most jacks require one person to manipulate the tree trunk and another to position the jack. Thus suitable tree jacks permitting a single person to harvest firewood, pulpwood, and the like from felled trees are not available.
When using chain saws to cut up tree trunks, it is difficult to cut squared blocks perpendicular to the tree axis supported by those prior art jacks that hold the tree at an angle to the ground. Also, it is dangerous to use a chain saw under conditions where the saw is not fully manually controlled with the user in a comfortable posture working upon tree trunks subject to unwanted turning or movement. Furthermore, a tree trunk must be held to avoid chain saw cuts that bind the sawblade, and in a position above ground so that the blade does not hit the ground with danger of losing control or at least damaging or wearing the blades with abrasives.
Nor are prior art timber jacks for cutting heavy logs particularly adapted to use in the woods in a tree felling site without site clearance and ground preparation. They are too heavy to carry into the woods by a single person. They are critical in placement, many being constructed for use on level ground. It is critical to balance and use the jacks so that a lifted tree trunk cannot inadvertently twist, turn or fall off the jack. Also they are apt to take up so much operating room that they cannot be used in many sites in thick woods where underbrush prohibits cleared worksites. Desired mechanisms for lifting trees must be light in weight and yet operable without significant efforts in balancing, leveling, or attachment to tree trunks.
U.S. Pat. No. 181,251, to H. A. Curtis, Aug. 22, 1876, for example, provides a general purpose lifting jack which could not be used at uneven ground timber felling sites without site preparation for anchoring two legs and positioning a crossbar to avoid tilt. Also a long jack handle that extends horizontally from the jack restricts the use to conditions where the site about a felled tree is cleared. Furthermore, a single person at the jack handle could not also reach to manipulate a chain about a tree trunk for engaging the jack, balancing it in position and initiating the lift of a heavy tree trunk.
J. H. Barret in U.S. Pat. No. 1,134,581, Apr. 6, 1915 grasps a tree trunk with claws and rotates a screw in a critically balanced crossbar to lift it. This jack is very restrictive in the size of trunk handled, and requires the cross bar holding the screw to be parallel with the ground for lifting a tree trunk vertically, which is not feasible at tree felling sites without preparation of a firm support surface or leveling ground such as usually encountered at sites in the woods or brush.
It is therefore a general object of this invention to remove the foregoing deficiencies of the prior art.
A more specific object of the invention is to provide a tree jack that can be used by a single person more ideally suited for harvesting firewood, pulpwood, or the like, with a chain saw at a variety of tree felling sites including those in heavy woods or brush.
Other objects, features and advantages of the invention will be found throughout the following description, claims and drawings.